Coating composition comprising submicron calcium carbonate-comprising particles, process to prepare same and use of submicron calcium carbonate-comprising particles in coating compositions

ABSTRACT

A coating composition comprising an aqueous dispersion of submicron natural ground calcium carbonate particles contained in a liquid binder, wherein the resultant coating may constitute either a clear coat or a glossing and opacifying coating, depending upon the presence of certain additives such as a mineral pigment (e.g., TiO 2 ). The composition is characterised in that comprises, in the case of a clear coating, at least one ground natural calcium carbonate having a median diameter of between 0.05 and 0.15 μm, while in the case of a glossing and opacifying coating, at least one ground natural calcium carbonate having a median diameter of between 0.05 and 0.3 μm and at least one pigment having a refractive index of greater than or equal to 2.5.

TECHNICAL FIELD

The present invention relates to coating compositions comprisingsubmicron natural ground calcium carbonate-comprising particles(hereafter SMGCC). The invention further relates to a process forpreparing coating compositions containing SMGCC, and to the use of SMGCCin coating compositions. The coating composition(s), depending upontheir composition, may be used to form either clear coatings, or elsethey may be formulated as glossing and opacifying coating compositions.The entire contents of provisional patent application No. 61/400,648filed Jul. 30, 2010 and entitled “Coating Composition ComprisingSubmicron Calcium Carbonate Comprising Particles, Process to PrepareSame and Use of Submicron Calcium Carbonate-Containing Particles inCoating Compositions” are specifically incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are photomicrographs of Omya XC-6600-34 CaCO₃; and

FIG. 2 is a series of particle size distribution curves containing datafor a series of samples whose D₉₈ value is <0.3 μm. The values for D₉₀,D₅₀ and D₂₀ for these samples can be determined by comparing the x andy-axis.

BACKGROUND AND DETAILED DESCRIPTION

The aqueous nanoparticle dispersion of this invention can be used tomake coatings and films for porous and non-porous substrates, such aspapers, non-woven materials, textiles, leather, wood, concrete, masonry,metals, house wrap and other building materials, fibreglass, polymericarticles, personal protective equipment (such as hazardous materialprotective apparel, including face masks, medical drapes and gowns andfiremen's turnout gear) and the like. Applications include papers andnon-woven materials, fibrous materials, films, sheets, composites andother articles, inks and decorative and industrial coatings, flock andother adhesives and personal care products such as skin care, hair careand nail care products, livestock and seed applications, and the like.

Any fibrous material can be coated, impregnated or otherwise treatedwith the compositions according to the invention by methods well knownto those skilled in the art, including carpets as well as textiles usedin clothing, upholstery, tents, awnings, airbags and the like. Suitabletextiles include fabrics, yarns and blends, whether woven, non-woven orknitted and whether natural, synthetic or regenerated. Examples ofsuitable textiles include cellulose acetate, acrylics, wool, cotton,jute, linen, polyesters, polyamides, regenerated cellulose (i.e., rayon)and the like.

The compositions, depending upon their intended application, may bedispersed in a variety of binders including, but not limited to,vinyl-acrylic, styrene-acrylic, acrylic dispersions, solution acrylics,alkyds (e.g., SOYA, TOFA, sunflower, etc.), polyurethanes dispersed ineither water or solvent, etc., hereinafter referred to as “bindermedia”.

Additionally, the compositions according to the invention can be used asadhesives or to augment or supplement adhesive types well known to thoseskilled in the art. Thus, in the application discussed above wherein thecompositions are used as adhesives or to augment or supplement variousknown adhesive types, particularly desirable properties can be obtainedby varying the type and amount of the aqueous nanoparticles used, alongwith choosing a complementary binder medium from one or more of thoselisted above, or by incorporating other binder media that would be wellknown to those of ordinary skill in this art.

As noted above, coatings containing the compositions according to theinvention may optionally be formulated as substantially transparentcoatings, i.e., typically referred to as ‘clear coats’, or alternatelyas coatings that serve a glossing and opacifying function. The clearcoating composites produced when the aqueous dispersions are applied anddried, exhibit excellent gloss and clarity. Moreover, so long as the D₉₈particle size of the substantially dispersed nanoparticles contained inthe coating composition is ≦350 nm, preferably ≦300 nm and the D₅₀ is≦200 nm, preferably ≦150 nm, the coatings obtained will be essentiallytransparent, provided of course that they are free or essentially freeof additional components which would comprise their transparencyproperties.

For purposes of exemplifying and not limiting, the invention, one usefulbinder medium for forming, e.g., clear coatings according to theinvention are polymers containing ester groups such as, for example,polyesters, polyester-based polyurethanes, polyester-based polyureas andpolyester-based polyamides. These various binders, however, have lessthan desirable water-resistance properties due to the hydrolysis groupcontained therein.

It has been determined, furthermore, that the water resistant propertiesof such polyester-based polyurethanes can be remarkably enhanced,without affecting the transparency properties of these materials to anysignificant degree, by combining with the polymer binder a substantiallydispersed nano-particle proton scavenger, such as natural ground calciumcarbonate-comprising particles. The resultant coating composition,therefore, which again is described only for exemplifying (and notlimiting) the invention, thus constitutes a hydrolytically stablepolyurethane nanocomposite comprising a solid polyester-polyurethanepolymer binder containing proton-scavenger nanoparticles in asubstantially dispersed form. One particular useful example of such aformulation would constitute a colloidally stable aqueous dispersioncomprising water, a polyester-polyurethane polymer binder andsubstantially dispersed proton scavenger nanoparticles such as SMGCC.

In the meaning of the present invention the term “substantiallydispersed” means that the nanoparticles are properly dispersed in theaqueous medium in order to prevent settling or syneresis of thenanoparticles. This is usually achieved via the addition of well-knowndispersants comprising homo- or copolymer chains. If necessary, thechains may be partially or completely neutralized by cations such assodium, lithium, magnesium, calcium, potassium or ammonium.

Coatings having the composition of the exemplary formulation describedabove, therefore, constitute polyurethane compositions which, e.g., haveimproved hydrolytic stability over prior art polyurethane compositions.As used herein the term polyurethane is used generically to describepolymers including oligomers (e.g., prepolymers) which contain theurethane group, i.e., —O—C(═O)—NH— regardless of how they are made. Asis well known, these polyurethanes can contain additional groups such asurea, allophanate, biuret, carbodiimide, oxazolidinyl, isocynurate,uretdione, alcohol, amine, hydrazide, siloxane, silane, ketone, olefin,etc., in addition to the urethane groups.

This invention includes, as noted herein the use of substantiallydispersed nanoparticles (referring to the primary crystallites orparticles of the proton scavenger and or the aggregates of the protonscavenger) of proton scavenger nanoparticles to enhance thewater-resistant (hydrolytic stability) of thermoplastic polyurethanescontaining polyester segments within the polyurethane polymer orprepolymer. Thermoplastic polyurethanes are made with the samecomponents as waterborne polyester polyurethanes (polyurethanedispersions in water) immediately below but typically the thermoplasticpolyurethanes have substantially less or no water-dispersibilityenhancing compound(s). In one embodiment the hydrolytically stablepolyurethane is a thermoplastic polyurethane. The technology for makingand using thermoplastic polyurethanes are well known and described forexample in U.S. Pat. No. 6,777,466 B2 and J. K. Backus et al.,“Polyurethanes,” in: Encyclopedia of Polymer Science and Engineering.Vol. 13, H F. Mark et al., Ed, pp. 243-303 (1988), the entire disclosureof which is incorporated herein by reference.

Furthermore, the invention in one embodiment relates to polyesterpolyurethanes which are derived from aqueous dispersions and which, whendried and cured, produce solid polyester segment containing polyurethaneproducts which are tough and, depending on the other ingredients present(e.g., absence of TiO₂ or other pigment), can be a transparent.

Further in accordance with this invention, it has been found that thesusceptibility of polyester polyurethanes to degrade through hydrolysiscan be essentially completely eliminated by incorporating into thepolymer a substantially dispersed nanoparticle (referring to theaggregate and/or the ultimate particles/crystallite) proton scavenger.

Certain materials are known to react with, bind to, or otherwise captureprotons, i.e., hydrogen ions, when exposed thereto in solid, liquidand/or gaseous media. Calcium carbonate, is a good example as are theother alkali and earth-alkali metal carbonates, i.e., Li₂CO₃, BeCO₃,MgCO₃, SrCO₃, BaCO₃, and RaCO₃. Other examples of carbonates which willscavenge protons include carbonates of Fe(II), Fe(III), Mn(II), Zn, Ag,Hg(I), Hg(II), Cu(II), Pb(II), Bi(III).

Calcium carbonate has the formula CaCO₃. It is a common substance foundin rock in all parts of the world, and is the main component of shellsof marine organisms, snails, pearls, and eggshells. Calcium carbonate isfound naturally as the following minerals and rocks: aragonite, calcite,vaterite or (μ-CaCO3), chalk, limestone, marble, travertine. The vastmajority of calcium carbonate used in industry is extracted by mining orquarrying. Pure calcium carbonate (e.g., for food or pharmaceuticaluse), can be produced from a pure quarried source (usually marble).Ground calcium carbonate (GCC) is produced through mechanical grindingof naturally occurring calcium carbonate rocks: marble, limestone andchalk. GCC in pigment formulations provides good rheology and highbrightness at low cost. Alternatively, crude calcium carbonate iscalcinated into calcium oxide (quicklime). Water is added to givecalcium hydroxide, and carbon dioxide is passed through this solution toprecipitate the desired calcium carbonate, known as precipitated calciumcarbonate (PCC). This process produces very pure calcium carbonatecrystals. The crystals can be tailored to a variety of different shapesand sizes, depending on the specific reaction process used. The threemain shapes of PCC crystals are aragonite, rhombohedral, andscalenohedral. Within each crystal type, the PCC process can controlmean particle size, size distribution, and surface area. Precipitatedcalcium carbonate is used as a mineral pigment throughout the world forpaper production. It is valued for its high brightness and lightscattering characteristics in paper filling and coating applications.

Other examples of inorganic compounds which will scavenge protonsinclude silicates of Ba, Ca, Mg, Al, Cr(III), Fe(II), Fe(III), Mn(II),Zn, Ag, Cu(II), Pb(II); sulfides of Fe(II), Mn(II), Zn, Ag, Hg(I),Hg(II), Cu(II), Pb(II), Bi(III), Sn(II); oxides and hydroxides of theabove metals; and hydroxyapatite, which is a naturally occurring mineralform of calcium apatite.

Examples of organic compounds which will scavenge protons include1,8-bis-(dimethylamino)naphthalene,1,8-bis(hexamethyltriaminophosphazenyl)naphthalene and2,6-di-tert-butylpyridine.

Any combination of the above scavenges may be used.

In accordance with this invention, it has been found that these protonscavengers materials form will substantially reduce or even completelyeliminate the susceptibility of polyester polyurethanes to degradethough hydrolysis without introducing any significant haze into thepolymer, but only if they are incorporated into the polymer in asubstantially dispersed nanoparticle and/or high surface area form.

In this regard, nanoparticles are typically obtained commercially inpowder or dispersion form, both aqueous and organic. Although theindividual/primary (crystallites for CaCO₃) particles in these productsmay be in the nano size range, these particles usually combine intolarger agglomerates in which the nanoparticles are relativelyclosely-packed with one another usually in three dimensions. Therefore,when these nanoparticle powders and dispersions are used to makenanoparticle-containing polymers, the nanoparticles remain in the formof these larger agglomerates. In other words, the nanoparticles are notsubstantially dispersed in the polymer mass. In accordance with thisinvention, it has been found that proton scavenger nanoparticles willsubstantially reduce or even completely eliminate the susceptibility ofpolyester polyurethanes to degrade though hydrolysis, but only if theyare incorporated into the polymer mass ultimately formed in asubstantially dispersed and/or high surface area form.

An example of substantially dispersed (but loosely aggregated having ahigh surface area (e.g. 41 m²/g) arrangement is shown in FIGS. 1A and1B. The primary nano crystallites of Omya XC-6600-34 from Omya formflocks of various shape and dimensions with a substantial portion of thesurface exposed to the matrix they are in. From this perspective, themost effective form of flocculation is a trains or chains of particles.Such an arrangement into relatively large floc particles can introducesome haze to the nanocomposites, but will still be effective inretarding ester hydrolysis because large portion of the nanoparticlessurfaces is exposed to the matrix.

In one embodiment where the ultimate particle/crystallite diameter issmall, desirably the D₅₀ is less than 1 micron, more desirably less than500 nm, more desirably less than 100 nm, and preferably less than 50 nm.In a similar embodiment, desirably the D₉₀ is less than 1 micron, moredesirably less than 500 nm, more desirably less than 100 nm, andpreferably less than 50 nm. In one embodiment, the nitrogen BET surfacearea is greater than 20 m²/g; more desirably greater than 30 m²/g; stillmore desirably greater than 35 m²/g and preferably about 40 or morem²/g.

In one embodiment, the particle size of the proton scavengernanoparticles when in the substantially dispersed form desired by thisinvention can vary widely, and essentially any particle size in thenanoparticle size range can be used. For the purposes of the presentinvention, nano particles and substantially dispersed nanoparticles aredefined as particles which have at least one of the three dimensions ofless than about 250 nm (D₉₀) but will normally be less than about 150nm. In other embodiments, the mean particle size will be about 100 nm orless (D₉₀), 75 nm or less, or even 50 nm or less. In some embodiments,the particle size may even be as low as 25 nm or less, 10 nm or less, oreven 5 nm or less. In general, the mean particle size, D₅₀, of thesesubstantially dispersed nanoparticles may be as large as 250 nm(nanometers) but will normally be less than 100 nm. Substantiallydispersed nanoparticles having a mean particle size of about 75 nm orless, more typically 50 nm or less, or even 40 nm or less areinteresting. In other embodiments, the mean particle size will be 30 nmor less, 25 nm or less, or even 10 nm or less. In some embodiments, theparticle size may even be as low as 5 nm or less, 2 nm or less, or even1 nm or less.

Particle size is usually characterized by particle size distribution,since all particles in a batch of particles do not have an identicalparticle size. Thus, in some embodiments of the invention, it isdesirable that the nanoparticle batch have a D₉₀ of less than 250 nm(i.e., 90% of volume of the particles in the batch have equivalentdiameters less than 250 nm). Nanoparticle batches with D₉₀′s of 150 nmor less, 100 nm or less, more typically 75 nm or less, or even 50 nm orless, 25 nm or less, 10 nm or less, or even 5 nm or less are especiallyinteresting.

Of particular interest are nanoparticle batches having D₉₀'s of about100 nm or less, and especially 75 nm or less, or even 50 nm or less,since nanoparticles of this size when substantially dispersed in apolymer matrix become essentially transparent to the naked eye.

The aqueous nanoparticle/polyester-polyurethane dispersions of thisinvention, both in prepolymer and chain extended form, can be used tomake coatings and films for porous and non-porous substrates such aspapers, non-woven materials, textiles, leather, wood, concrete, masonry,metals, house wrap and other building materials, fiberglass, polymericarticles, personal protective equipment (such as hazardous materialprotective apparel, including face masks, medical drapes and gowns, andfiremen's turnout gear), and the like. Applications include papers andnon-wovens, fibrous materials, films, sheets, composites, and otherarticles, inks and printing binders, flock and other adhesives, andpersonal care products such as skin care, hair care, and nail careproducts, livestock and seed applications, and the like.

Any fibrous material can be coated, impregnated or otherwise treatedwith the compositions of this invention by methods well known to thoseskilled in the art, including carpets as well as textiles used inclothing, upholstery, tents, awnings, air bags, and the like. Suitabletextiles include fabrics, yarns, and blends, whether woven, non-woven,or knitted, and whether natural, synthetic, or regenerated. Examples ofsuitable textiles include cellulose acetate, acrylics, wool, cotton,jute, linen, polyesters, polyamides, regenerated cellulose (Rayon), andthe like.

Compositions of this invention can also be used to produce articles madeof stand-alone films and objects such as personal protective equipment.Examples of protective items include gloves and condoms.

In addition, the compositions of this invention can be used as adhesivesor to augment or supplement adhesive types well known to those skilledin the art. For example, particular adhesive properties can be achievedby varying type and amount of isocyanates, type, amount, and molecularweight of polyols, and the amount of poly(alkylene oxide) side chainunits.

The polyester-polyurethane nanoparticle composites produced when theaqueous dispersions of this invention are applied and dried, whether ornot the polyester-polyurethane is chain extended, exhibit exceptionalresistance to degradation by hydrolysis, in particular a resistance tohydrolysis comparable to that of the much more expensive polycarbonatepolyurethane resins. Moreover, so long as the D₉₀ particle size of thesubstantially dispersed nanoparticles used is ≦75 nm, preferably ≦50 nmor even ≦40 nm, the polyurethanes obtained will be essentiallytransparent, provided of course that they are free or essentially freeof other materials which would compromise their transparency properties.

Finally, the principles of the present invention can be applied to othertechnologies for manufacturing aqueous polyurethane dispersions. Forexample, this invention can be applied to the technique formanufacturing breathable polyurethane dispersions (i.e. dispersionswhich form layers of breathable polyurethanes) described in U.S. Pat.No. 6,897,281, as well as to the technique for manufacturing core-shellpolyurethane dispersions described in U.S. Published Patent ApplicationNo. 20050004306. The disclosures of the above patent and publishedapplications are incorporated herein by reference.

Polyurethanes based on polyester macroglycols are known to besusceptible to hydrolysis. The hydrolytic stability of the improvedproduct is attributed to the presence of a proton scavenger in highlydispersed form having significant surface area (increasing theprobability that the proton scavenger will be able to scavenge protonicspecies before the cause hydrolytic chain scission in the polyesterportion of the polyurethane). The polyurethane can be in the form of afilm, coating or shaped article. The proton scavenger is preferably aninorganic carbonate salt such as calcium carbonate. If the aggregates ofthe proton scavenger are small relative to the wavelength of light thepolyurethane composition will be substantially transparent to visiblelight. If the proton scavenger, e.g. calcium carbonate, is comprised ofloosely aggregated primary crystallites, that are in the 5-100 nanometerweight average diameter, it will have high surface area (e.g. >40 m²/g)will be effective at scavenging protons.

In order to further exemplify the clear coatings formulated according tothe invention, several working examples of such clear coat formulationsare provided below. In these examples, the following raw materials wereused:

-   -   DOW—SG30 Acrylic Latex (binder medium)    -   Bayhydrol 110—Polyurethane Dispersion (binder medium)    -   Deionized Water    -   Various Omya experimental SM-GCC slurries.

In addition, the following analytical and testing procedures were usedin carrying out these examples:

-   -   Gloss was measured at 20°, 60°, and 75° angles utilizing a Micro        TriGloss unit from BYK-Gardner, catalog #4446    -   Sheen at 85° angle utilizing a Micro TriGloss unit from        BYK-Gardner, catalog #4446    -   Solids Content—total solids were measured by Moisture/Solids        Analyzer Toledo HB 43 (Mettler Toledo Corporation)    -   pH Measurements—pH readings were taken using pH 510 Meter, a pH        meter from BYK-Gardner, Catalog #PH-2643.    -   Gloss/Haze. The preferred evaluation of haze is visual because        perceived haze and clarity are one of the most important        properties of coatings and other articles. Haze can also be        measured by objective instrumental means. Examples include the        method described in ASTM D 1003-07 “Standard Test Method for        Haze and Luminous Transmittance of Transparent Plastics”,        measurement of gloss at different angles, measurement of L,a,b        values, and also other methods described in ASTM Guide        E179-96(2003) “Standard Guide for Selection of Geometric        Conditions for Measurement of Reflection and Transmission        Properties of Materials”, D1455 “Test Method for 60-deg Specular        Gloss of Emulsion Floor Polish”, D1746 “Test Method for        Transparency of Plastic Sheeting”, D4039 “Test Method for        Reflection Haze of High-Gloss Surfaces”, D4061 “Test Method for        Retroreflectance of Horizontal Coatings” and D523 “Test Method        for Specular Gloss”.

Preparation of a Clear Gloss Coating Containing Calcium CarbonateNanoparticle Dispersion

In each case an aqueous dispersion of substantially dispersed calciumcarbonate nanoparticles was produced by from the following ingredients:

INGREDIENTS USED IN EXAMPLE 1

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 59.7 Water12.3 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 2

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 61.2 Water10.8 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 3

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 62.2 Water9.8 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 4

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 61.7 Water10.3 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 5

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 61.2 Water10.8 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 6

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 62.1 Water9.9 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 7

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 60.2 Water11.8 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 8

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 61.3 Water10.7 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 9

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 60 Water12 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

INGREDIENTS USED IN EXAMPLE 10

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 60.6 Water11.4 DOW - SG30 Acrylic Latex binder 100 TOTAL 172

TABLE 1 GLOSS MEASUREMENT Malvern Malvern 75° 20° 60° 85° D(50) D(98) SG30 93 63.3 83.3 92.5 N/A N/A Control Example 1 88.4 33 70.7 89.9 0.120.3 Example 2 83.7 19 60.2 91 0.12 0.4 Example 3 85.1 22.6 61.5 87.20.13 0.5 Example 4 83.2 17.7 57.8 90.5 0.13 0.3 Example 5 88.1 33.1 69.689 0.12 0.4 Example 6 83.6 16.6 56.5 91.4 0.13 0.5 Example 7 80.3 14.553 88.7 0.12 0.3 Example 8 88.4 36.6 71.9 89.8 0.13 0.4 Example 9 82.216.8 54.2 88.5 0.13 0.5 Example 81.5 16.2 53.9 90.2 0.13 0.6 10

The samples made with Dow SG-30 all acrylic latex were prepared using aPremier Mill Model #CM 100 high speed dissolver with a 2.5 in blade.They were dispersed for 30 minutes at 900 rpm.

INGREDIENTS USED IN EXAMPLE 11

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 2.3Bayhydrol 110 PUD binder 75 TOTAL 77.3

INGREDIENTS USED IN EXAMPLE 12

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 2.4Bayhydrol 110 PUD binder 75 TOTAL 77.4

INGREDIENTS USED IN EXAMPLE 13

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 2.4Bayhydrol 110 PUD binder 75 TOTAL 77.4

INGREDIENTS USED IN EXAMPLE 14

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 2.8Bayhydrol 110 PUD binder 75 TOTAL 77.8

INGREDIENTS USED IN EXAMPLE 15

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 2.8Bayhydrol 110 PUD binder 75 TOTAL 77.8

INGREDIENTS USED IN EXAMPLE 16

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 4.6Bayhydrol 110 PUD binder 75 TOTAL 79.6

INGREDIENTS USED IN EXAMPLE 17

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 4.8Bayhydrol 110 PUD binder 75 TOTAL 79.8

INGREDIENTS USED IN EXAMPLE 18

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 4.8Bayhydrol 110 PUD binder 75 TOTAL 79.8

INGREDIENTS USED IN EXAMPLE 19

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 5.6Bayhydrol 110 PUD binder 75 TOTAL 80.6

INGREDIENTS USED IN EXAMPLE 20

Ingredient Wt., g Omya experimental SMGCC (Calcium Carbonate) 5.6Bayhydrol 110 PUD binder 75 TOTAL 80.6

TABLE 2 Bayhydrol with 5% GCC loading GLOSS MEASUREMENT 20° 60° 85°Bayhydrol 110 67.5 90.9 95.9 (Control) Example 11 65.8 87.2 96.1 Example12 74.1 88.6 97.9 Example 13 71.3 88.4 97.7 Example 14 72.5 88.5 98Example 15 75.6 88.4 97.8

TABLE 3 Bayhydrol with 10% GCC loading GLOSS MEASUREMENT 20° 60° 85°Bayhydrol 110 67.5 90.9 95.9 (Control) Example 16 60 87 95 Example 1764.2 89.9 95.5 Example 18 64.9 86.6 95.5 Example 19 64.3 87 95.8 Example20 62.1 86.3 95.7

The samples made with Bayhydrol 110 were prepared using a Speed MixerModel # DAC 150.1 FVZ-K. They were dispersed for 1 min at 2500 rpm.

Turning next, then, to a discussion of an alternate embodiment of thepresent invention wherein the aqueous nanoparticle dispersions describedherein are utilized in forming glossing and opacifying coatingcompositions, it is noted that mineral pigments are widely used in knownglossing and opacifying coating systems, not only to decreaseformulation costs but further to improve certain properties of thecoating formulation during its preparation or storage, or during orfollowing its application to a substrate. In the realm of paintformulations, coating systems almost invariably implement titaniumdioxide.

In the context of paint applications, titanium dioxide (TiO₂) iscommonly used, particularly in its rutile form, for providingsignificant opacity or hiding power. Titanium dioxide pigments marketedfor use in paint formulation are well known to present a narrow particlesize distribution along with a median particle diameter of between 0.2and 0.6 μm, depending on the material and the mean particle sizemeasurement method. Zinc sulphide and zinc oxide are similarly employed.

Titanium dioxide suffers however from being relatively high in cost,resulting in a continuing desire to find lower-cost TiO₂ partialreplacement pigments that do not translate in a reduction of optical andother coating composition properties.

GB1404564 describes ultrafine natural calcium carbonate filled paintsand pigments, wherein said natural calcium carbonate has a particlediameter of from 0.5 to 4 μm and is employed to partially replacetitanium dioxide. In this vein, Imerys has commercialised Polcarb, saidto be suitable for glossing paint formulations, which has a meanparticle size of 0.9 μm. However, such natural calcium carbonateproducts do not allow the replacement of a part of TiO₂ in glossingpaint formulation having a pigment volume concentration below thecritical pigment volume concentration without loss of gloss or opacity.

For the purpose of describing the glossing and opacifying coatingcompositions according to the present invention, the pigment volumeconcentration (PVC) is understood to refer to the fraction, quoted in %,of pigment volume relative to the total volume of the pigment plus theother components of the formulation, i.e., it accounts for the pigmentvolume relative to the total formulation volume.

The critical pigment volume concentration (CPVC) is defined as thepigment volume concentration whereupon the resin component of thecoating formulation is no longer sufficient to entirely coat all of thepigment particles in a coating. It is well known that above the CPVC,formulations generally provide a matt finish. By contrast glossy paintformulations implement a PVC that is below the CPVC.

U.S. Pat. No. 5,171,631 discloses a coating composition for developinghiding on a suitable substrate, the coating composition having a pigmentvolume concentration (PVC) up to a critical pigment volume concentration(CPVC) and a pigment system comprising about 70-98% by volume oftitanium dioxide and about 2-30% by volume of an aluminium trihydrate(ATH) spacer/extender pigment having a medium particle size of about 0.2microns. FIG. 1 of U.S. Pat. No. 5,171,631 shows a D₉₈/D₅₀ ratio valueof approximately 2.7, which corresponds to a relatively narrow particlesize distribution. Although it is stated that, provided this ATH has amedian particle size and particle size distribution generally similar tothe median particle size and particle size distribution curve of TiO₂, aportion of TiO₂ may be replaced with an equal volume of ATH with no lossof hiding, FIG. 2 of U.S. Pat. No. 5,171,631 shows that theATH-TiO₂-comprising paint formulations generally fail to achieve thesame opacity values as the control paint formulation comprising TiO₂alone.

Natural ground calcium carbonate as opposed to its syntheticcounterpart, precipitated calcium carbonate (PCC), generally suffersfrom a broad particle size distribution and irregular particle shapes.Indeed, as natural ground calcium carbonate is prepared by the grindingdown of mined calcite, marble, chalk or limestone-containing stones, itis difficult to ensure that these stones are ultimately fractioned toform fine particles having a very uniform particle size.

By contrast, PCC is formed by a process of building crystals aroundnucleation sites. Control of nucleation and particle size development,particularly in the size domain under a few micrometers, during PCCprecipitation has, over the years, become a well studied science and PCCparticles having small and very uniform particle sizes and shapes arenow widely available. As in U.S. Pat. No. 5,171,631, the advantages ofemploying a uniform particle size product as a titanium dioxide spacerare alluded to in the publication made athttp://www.specialtyminerals.com/specialty-applications/specialty-markets-for-minerals/paint-and-coatings/precipitated-calcium-carbonate-pcc-in-paint/:“precipitated calcium carbonate (PCC) is most commonly used in paint asan extender for titanium dioxide, or TiO₂. The small and narrowlydistributed PCC particles help space the individual TiO₂ particles andmaximize their hiding power.” In this domain, Specialty Mineralsadvertises Albafil PCC, a fine, 0.7 micron prismatic calcite, and arange of ultrafine or nano PCCs, namely Calofort S PCC, Calofort U PCC,Ultra-Pflex PCC and Multifex MM PCC, each having a median diameter of0.07 micron.

In view of the above-discussed teachings found in the prior art, it wasremarkable that the present inventors found that a ground naturalcalcium carbonate that is finer than ground natural calcium carbonateproducts previously offered in this domain, may be used to form anaqueous nanoparticle dispersion in one or more of the binder systemsdescribed above for use in forming a variety of (1) clear-coat coatingcompositions (see the discussion above), as well as serving as (2) aTiO₂ replacement or complementary pigment in the formation of glossingand opacifying coating compositions, even in the case when this groundnatural calcium carbonate features a relatively broad particle sizedistribution and/or a median diameter that is different from that ofTiO₂. By contrast to the results of U.S. Pat. No. 5,171,631 achievedwith ATH, the ground natural calcium carbonate employed in the presentinvention not only more fully maintains the gloss and opacity of thepaint formulation when used to replace part of the formulation TiO₂ atconstant PVC, it may even lead to a gloss and/or opacity improvement.

One embodiment of a glossing and opacifying coating compositionaccording to the invention is a composition having a PVC of from 5% upto the CPVC and characterised in that comprises at least one groundnatural calcium carbonate having a median diameter (d50 (Mal)) ofbetween 0.05 and 0.3 (hereafter submicron ground natural calciumcarbonate, SMGCC), and at least one pigment having a refractive index ofgreater than or equal to 2.5.

For the purpose of describing the glossing and opacifying coatingcompositions of the present application, CPVC was determined accordingto the measurement method given in the examples section below.

Moreover, for the purpose of further describing the glossing andopacifying coating compositions according to the present invention, themedian diameter (d50 (Mal)) and d98 (Mal) were measured according to themeasurement method provided in the examples section below.

Another object of the present invention resides in a process to preparea glossing and opacifying coating composition having a PVC of from 5% upto the CPVC, characterised in that:

a) at least one ground natural calcium carbonate (SMGCC) having a D₅₀(Mal) of between 0.05 and 0.3 μm is provided;

b) at least one pigment having a refractive index of greater than orequal to 2.5 is provided;

c) at least one resin (binder) is provided;

d) the SMGCC of step a) is mixed with the pigment of step b) and theresin of step c).

A third object of producing the glossing and opacifying coatingsaccording to the present invention lies in the use of at least oneground natural calcium carbonate having a d50 (Mal) of between 0.05 and0.3 μm, in a coating composition comprising at least one pigment havinga refractive index of greater than or equal to 2.5, characterised inthat for a coating composition having a constant PVC in the range offrom 5% up to the CPVC, the gloss and/or opacity of the composition isequal to or greater than the gloss and/or opacity of the samecomposition implementing the pigment having a refractive index ofgreater than or equal to 2.5 in place of the ground natural calciumcarbonate having a d50 of between 0.05 and 0.3 μm.

The gloss of a coating composition applied to a substrate was measuredaccording to the measurement method provided in the examples sectionbelow.

The opacity of a coating composition applied to a substrate was measuredaccording to the measurement method provided in the examples sectionbelow.

In order to more thoroughly describe the formulation of glossing andopacifying coating compositions according to the invention, thefollowing examples are provided below.

A first embodiment of such a glossing and opacifying coating comprises acoating composition having a PVC of from 5% up to the CPVC andcharacterised in that comprises at least one ground natural calciumcarbonate having a median diameter (D₅₀ (Mal)) of between 0.05 and 0.3μm (hereafter submicron ground natural calcium carbonate, SMGCC), and atleast one pigment having a refractive index of greater than or equal to2.5. Preferably, the coating composition has a PVC of from 15 to 25%.

Preferably, the SMGCC has a median diameter (D₅₀ (Mal)) of between 0.1and 0.3 μm.

In another embodiment, the SMGCC has a D₉₈/D₅₀ (Mal) of greater than 3.As indicated above and in contrast to the prior art, this ground naturalcalcium carbonate may, in an optional embodiment, have a particle sizedistribution that is broad and dissimilar to the particle sizedistribution said pigment having a refractive index of greater than orequal to 2.5 employed in the composition. Indeed, even a bi- ormultimodal SMGCC particle size distribution may be envisioned.

In a preferred embodiment, said SMGCC has a D₉₈ of less than or equal to1 μm, more preferably of less than or equal to 0.8 μm, even morepreferably of less than or equal to 0.6 μm, and even more preferably ofless than or equal to 0.4 μm.

Preferably, the SMGCC has a refraction index of approximately 1.5 to1.7.

In another preferred embodiment, the pigment having a refractive indexof greater than or equal to 2.5 is selected from one or more of thefollowing: titanium dioxide and/or zinc sulphide and/or zinc oxide. In amore preferred embodiment, the pigment having a refractive index ofgreater than or equal to 2.5 is titanium dioxide. In such a case, it ispreferred that the titanium dioxide:SMGCC weight ratio is of 70:30 to98:2, and it is even more preferred that the titanium dioxide:SMGCCweight ratio is of 85:15 to 90:10.

In an alternate embodiment, the pigment contributing to the PVC of thecomposition is a mixture of at least one pigment having a refractiveindex of greater than or equal to 2.5, SMGCC and one or more of thefollowing: clay, talc, magnesium carbonate, PCC, barium sulphate, micaand bentonite. In the case where magnesium carbonate is implemented incombination with SMGCC, this may be in the form of a dolomite.

This coating composition is characterised in that when all of said SMGCCis replaced by said pigment having a refractive index of greater than orequal to 2.5 while maintaining a constant PVC value in the range of from15% up to the CPVC, the gloss of the SMGCC-comprising composition iswithin 10% of the gloss of the composition wherein the SMGCC is fullyreplaced by said pigment having a refractive index of greater than orequal to 2.5. Preferably, the gloss of the SMGCC-comprising compositionis within 5%, and more preferably within 3%, of the gloss of thecomposition having only said pigment having a refractive index ofgreater than or equal to 2.5.

As shown in the examples below, it is not necessary that the SMGCC havea median diameter (D₅₀ (Mal)) that is equivalent to the median diameter(D₅₀ (Mal)) of said pigment having a refractive index of greater than orequal to 2.5, though this embodiment is not excluded from the presentinvention. The median diameter (D₅₀ (Mal)) of SMGCC may differ from themedian diameter (D₅₀ (Mal)) of said pigment having a refractive index ofgreater than or equal to 2.5 by up to approximately 0.4 μm.

As also demonstrated by the examples below, said SMGCC may feature abroad and even non-uniform particle size distribution relative to thedistribution of the pigment having a refractive index of greater than orequal to 2.5 is, though again this does not exclude the case where theparticle size distributions of SMGCC and the pigment having a refractiveindex of greater than or equal to 2.5 is are similar in breadth.

Alternatively, the gloss of the SMGCC-comprising composition may beincreased by at least 1% relative to the gloss of the compositionwherein the SMGCC is fully replaced by the pigment having a refractiveindex of greater than or equal to 2.5. Relative to this embodiment, thegloss of the SMGCC-comprising composition is preferably increased by atleast 5% relative to the gloss of the composition wherein the SMGCC isfully replaced by the pigment having a refractive index of greater thanor equal to 2.5.

In a preferred embodiment, said SMGCC is dispersed with one or moredispersants. Conventional dispersants known to the skilled person can beused. The dispersant can be anionic, cationic or non-ionic. A preferreddispersant is polyacrylic acid.

The coating compositions according to the present invention (i.e., whenused in forming the clear coatings as well as glossing and opacifyingcoatings) may be applied to a variety of substrates as discussed above,including but not limited to, concrete, wood, paper, metal and board.

In a preferred embodiment, the coating composition is applied to asubstrate in an amount so as to form a layer having a thickness ofbetween 100 and 400 um.

Following application to a substrate, a glossing and opacifying coatingcomposition according to the invention preferably provides a glossmeasured at 60° of greater than 70%. Furthermore, following applicationto a substrate, the coating composition preferably provides an opacity(contrast ratio) of greater than 97%.

The present coating compositions may further include one or more of thefollowing: optical brightener, resin (such as a latex or acrylate-basedbinder, preferably in the form of an aqueous emulsion), defoamer,thickener, solvent, glycol ethers and dispersant. Preferably, thecoating composition has a Brookfield viscosity of from 200 to 500 mPa·s,as measured according to the measurement method provided in the examplesbelow.

Process for Preparing a Glossing/Opacifying Coating Composition inAccordance with the Present Invention

The process results in the preparation of a coating composition having aPVC of from 5% up to the CPVC, characterised in that:

a) at least one ground natural calcium carbonate (SMGCC) having a D₅₀ ofbetween 0.05 and 0.3 μm is provided;

b) at least one resin (binder) is provided;

c) the SMGCC of step a) is mixed with the resin of step b).

The SMGCC of step a) may be provided in the form of an aqueoussuspension, an aqueous dispersion or as a dry powder. In a preferredembodiment, the SMGCC of step a) is provided in the form of an aqueoussuspension or dispersion.

The resin is preferably a latex and/or acrylate-based binder, saidacrylate-based binder preferably being in the form of an aqueousemulsion.

Use of SMGCC in Glossing/Opacifying Coating Compositions

Another object of the present invention lies in the use of at least oneground natural calcium carbonate having a D₅₀ (Mal) of between 0.05 and0.3 μm, in a glossing/opacifying coating composition, characterised inthat for a coating composition having a constant PVC in the range offrom 15% up to the CPVC, the gloss and/or opacity of the composition isequal to or greater than the gloss and/or opacity of the samecomposition implementing TiO₂ in place of said ground natural calciumcarbonate having a d50 of between 0.05 and 0.3 μm.

Another object of the present invention is the production of a paintcomprising the glossing/opacifying coating composition of the invention.

EXAMPLES OF GLOSSING/OPACIFYING COATING COMPOSITIONS

Suspension or Dispersion Solids Content (% Equivalent Dry Weight)

The weight of the solid material in a suspension or dispersion isdetermined by weighing the solid material obtained by evaporating theaqueous phase of suspension and drying the obtained material to aconstant weight.

Particle Size Distribution (Mass % Particles with a Diameter<X) andMedian Grain Diameter (d₅₀ (Sedi), d₅₀ (Mal) and d₉₈ (Mal)) ofParticulate Material

Weight median grain diameter (d₅₀ (Sedi)) and grain diameter massdistribution of a particulate material are determined via thesedimentation method, i.e. an analysis of sedimentation behavior in agravimetric field. The measurement is made with a Sedigraph™ 5100.

The method and the instrument are known to the skilled person and arecommonly used to determine grain size of fillers and pigments. Themeasurement is carried out in an aqueous solution of 0.1% by weight ofNa₄P₂O₇. The samples were dispersed using a high-speed stirrer andultrasonic means.

Weight median grain diameter (d₅₀ (Mal)) was evaluated using a MalvernMastersizer 2000 (Frauenhofer). The d₉₈ (Mal) value, measured using aMalvern Mastersizer 2000 (Frauenhofer), indicates a diameter value suchthat 98% by weight of the particles have a diameter of less than thisvalue.

BET Specific Surface Area (m²/g)

BET specific surface area values were determined using nitrogen and theBET method according to ISO 9277.

Gloss of a Coated Surface

Gloss values are measured at the listed angles according to DIN 67 530on painted surfaces prepared with a coater gap of 150 and 300 μm oncontrast cards.

Contrast Ratio (Opacity) of a Coated Surface

Contrast ratio values are determined according to ISO 6504/3 at aspreading rate of 7.5 m²/l.

Suspension or Dispersion Brookfield-Viscosity (mPas)

Brookfield-viscosities are measured with a Brookfield DV-II Viscometerequipped with a LV-3 spindle at a speed of 100 rpm and room temperature(20±3° C.).

Pigment Volume Concentration (PVC, %)

The pigment volume concentration is calculated as described in Section6.2.3 of the book entitled “Fuellstoff' by Detlef Gysau (Hannover:Vincentz Network 2005).

Total sum by volume of all pigments+extenders in paint×100%

Total sum by volume of all solid ingredients in paint

Critical Pigment Volume Concentration (CPVC, %)

The critical pigment volume concentration is a well known concentrationwidely used in the paint industry. It is generally considered torepresent the point at which there is just enough resin to wet thepigment particles, and changes to the PVC near to the CPVC can result inabrupt changes to coating properties, such as porosity and gloss. TheCPVC and its measurement method according to ISO 4618 are discussed inSection 6.2.4 of the book entitled “Fuellstoff” by Detlef Gysau(Hannover: Vincentz Network 2005).

Materials:

SMGCC

SMGCC dispersions used in the following examples are natural groundcalcium carbonate (marble from Vermont) having the median particle sized₅₀ and particle size characteristics given in the table below.

TABLE 4 d₉₈ d₅₀ Solids SSA % < % < (Mal) (Mal) d₉₈/d₅₀ SMGCC (%) (m²/g)% < 1 μm 0.5 μm 0.2 μm μm μm (Mal) 1 60 36.0 98.3 94.3 65.1 0.53 0.62 52 49 37.7 98.3 94.8 65.7 0.55 0.122 4.5 3 46 38.6 97.7 94.8 69.5 0.310.128 2.4

Titanium Dioxide

The titanium dioxide employed in the examples herebelow consists of 95%by weight of pure rutile TiO₂, with the remaining weight being accountedfor in a surface treatment of alumina, zirconia and an organic surfacetreatment agent. This pigment features a d50 (Mal) of approximately 0.55μm and is provided in the form of an aqueous paste having a 75% solidscontent. By scanning electron microscope imaging, the particles appearto be in the range of 0.2 to 0.25 μm. The refractive index of TiO₂ is2.7.

EXAMPLE 21

The following example illustrates a comparative paint composition andpaint compositions according to the invention. The formulated paintswere applied to a contrast card in the necessary amounts in order tomeasure both gloss and opacity.

TABLE 5 Example 1 2 3 4 Comparison (CO)/Invention (IN) CO IN IN IN Paintcomposition formulation Water (g) 133.6 119.8 110.9 108.0 Hydrophilic6.4 6.5 6.5 6.5 copolymer dispersant, 50% solids content (g) Ammonia, 44 4 4 24% active content (g) Paraffin-based 7 7 7 7 mineral oil mixturecontaining silicone (g) Rheotech 200 15 15 15 15 thickener from Coatex(g) Propylene 10 10 10 10 glycol (g) Butyl diglycol 5 5 5 5 (g)Dipropylene 10 10 10 10 Glycol n-Butyl Ether (g) Ester alcohol 9 9.119.11 9.11 with Mw = 216 g/mol (g) Acrylate 550 557 557 557 binderemulsion, 48% active content (g) TiO₂ (g) 250 218 218 218 SMGCC1 (g) 39SMGCC2 (g) 48 SMGCC3 (g) 51 % weight TiO₂ 0 12 12 12 replaced by SMGCCPVC (%), 21.1 21.1 21.1 21.1 approx. Properties on application of thepaint formulation Contrast ratio at 7.5 m2/l spreading rate (%) 98.698.5 98.6 98.5 Gloss obtained using a coater gap of 150 μm 20° 51.8 50.650.6 55.7 60° 80.3 79.7 79.7 81.7 85° 93.6 95.9 96.2 96.8 Gloss obtainedusing a coater gap of 150 μm 20° 55.6 52.4 54.7 56.8 60° 79.4 78.7 80.180.5 85° 95.6 95.7 96.5 95.8

The results set forth in table 5 above demonstrate that replacing a partof TiO₂ with the SMGCC according to the invention, and having d98/d50values ranging from 2.4 to 5, results in coatings having essentially thesame opacity (contrast ratio) as the comparison formulation having equalPVC but only TiO₂. Gloss values are observed to be equivalent orimproved relative to the comparison formulation having equal PVC butonly TiO₂.

1. A clear coat composition comprising an aqueous nanoparticledispersion, wherein the nanoparticles are substantially dispersed andhave a mean particle size D₅₀ of less than 1 micron, preferably of lessthan 500 nm, more preferably of less than 100 nm, and even morepreferably of less than 50 nm.
 2. The clear coat composition accordingto claim 1, wherein the nanoparticles have a particle size D₉₀ of lessthan 1 micron, preferably of less than 500 nm, more preferably of lessthan 100 nm, and even more preferably of less than 50 nm.
 3. The clearcoat composition according to claim 1, wherein the nitrogen BET surfacearea of the nanoparticles is greater than 20 m²/g, preferably greaterthan 30 m²/g, more preferably greater than 35 m²/g, and even morepreferably about 40 m²/g.
 4. The clear coat composition according toclaim 1, wherein the nanoparticles are selected from the groupcomprising calcium carbonate, other alkali and earth-alkali carbonatesincluding Li₂CO₃, BeCO₃, MgCO₃, SrCO₃, BaCO₃, and RaCO₃; carbonates ofFe(II), Fe(III), Mn(II), Zn, Ag, Hg(I), Hg(II), Cu(II), Pb(II), Bi(III);silicates of Ba, Ca, Mg, Al, Cr(III), Fe(II), Fe(III), Mn(II), Zn, Ag,Cu(II), Pb(II); sulfides of Fe(II), Mn(II), Zn, Ag, Hg(I), Hg(II),Cu(II), Pb(II), Bi(III), Sn(II); oxides and hydroxides of the abovemetals; hydroxyapatite; organic compounds including1,8-bis-(dimethylamino)naphthalene,1,8-bis(hexamethyltriaminophosphazenyl)naphthalene and2,6-di-tert-butylpyridine; or any combination of the aforementioned. 5.The clear coat composition according to claim 4, wherein the calciumcarbonate is either a ground calcium carbonate derived from grinding ofchalk, limestone, marble, or is precipitated calcium carbonate, andpreferably is ground calcium carbonate, and more preferably is submicronground calcium carbonate (SMGCC).
 6. The aqueous nanoparticle dispersionaccording to claim 1, wherein the nanoparticles are dispersed in atleast one binder including vinyl-acrylic, styrene-acrylic, acrylicdispersions, solution acrylics, alkyds, polyurethanes dispersed eitherin water or solvent, polymers containing ester groups includingpolyesters, polyester-based polyurethanes, polyester-based polyureas andpolyester-based polyamides, preferably the binder is apolyester-polyurethane polymer binder.
 7. The clear coat compositionaccording to claim 1, wherein the substantially dispersed nanoparticlescontained in the coating composition have a D₉₈ particle size of ≦350nm, preferably ≦300 nm, and a D₅₀ particle size of ≦200 nm, preferably≦150 nm.
 8. A glossing and opacifying coating composition comprising anaqueous nanoparticle dispersion, wherein the nanoparticles aresubstantially dispersed and have a mean particle size D₅₀ of less than 1micron, preferably of less than 500 nm, more preferably of less than 100nm, and even more preferably of less than 50 nm.
 9. The glossing anopacifying coating composition according to claim 8, wherein thenanoparticles have a particle size D₉₀ of less than 1 micron, preferablyof less than 500 nm, more preferably of less than 100 nm, and even morepreferably of less than 50 nm.
 10. The glossing an opacifying coatingcomposition according to claim 8, wherein the nitrogen BET surface areaof the nanoparticles is greater than 20 m²/g, preferably greater than 30m²/g, more preferably greater than 35 m²/g, and even more preferablyabout 40 m²/g.
 11. The glossing an opacifying coating compositionaccording to claim 8, wherein the nanoparticles are selected from thegroup comprising calcium carbonate, other alkali and earth-alkalicarbonates including Li₂CO₃, BeCO₃, MgCO₃, SrCO₃, BaCO₃, and RaCO₃;carbonates of Fe(II), Fe(III), Mn(II), Zn, Ag, Hg(I), Hg(II), Cu(II),Pb(II), Bi(III); silicates of Ba, Ca, Mg, Al, Cr(III), Fe(II), Fe(III),Mn(II), Zn, Ag, Cu(II), Pb(II); sulfides of Fe(II), Mn(II), Zn, Ag,Hg(I), Hg(II), Cu(II), Pb(II), Bi(III), Sn(II); oxides and hydroxides ofthe above metals; hydroxyapatite; organic compounds including1,8-bis-(dimethylamino)naphthalene,1,8-bis(hexamethyltriaminophosphazenyl)naphthalene and2,6-di-tert-butylpyridine; or any combination of the aforementioned. 12.The glossing an opacifying coating composition according to claim 11,wherein the calcium carbonate is either a ground calcium carbonatederived from grinding of chalk, limestone, marble, or is precipitatedcalcium carbonate, and preferably is ground calcium carbonate, and morepreferably is submicron ground calcium carbonate (SMGCC).
 13. Theglossing an opacifying coating composition according to claim 8, whereinthe nanoparticles are dispersed in at least one binder includingvinyl-acrylic, styrene-acrylic, acrylic dispersions, solution acrylics,alkyds, polyurethanes dispersed either in water or solvent, polymerscontaining ester groups including polyesters, polyester-basedpolyurethanes, polyester-based polyureas and polyester-based polyamides,preferably the binder is a polyester-polyurethane polymer binder. 14.The glossing an opacifying composition according to claim 8, having apigment volume concentration (PVC) of from 5% up to the critical pigmentvolume concentration (CPVC) and comprising at least one ground calciumcarbonate having a D₅₀ (Mal) of between 0.05 and 0.3 μm, and at leastone pigment having a refractive index of greater than or equal 2.5. 15.The glossing an opacifying composition according to claim 14, whereinthe ground calcium carbonate has a D₅₀ (Mal) of between 0.1 and 0.3 μm.16. The glossing an opacifying composition according to claim 8, whereinthe ground calcium carbonate has a D₉₈/D₅₀ (Mal) of greater than
 3. 17.The glossing an opacifying composition according to claim 16, whereinthe ground calcium carbonate has a D₉₈ of less than or equal to 1 μm,preferably of less than or equal to 0.6 μm, more preferably of less thanor equal to 0.4 μm.
 18. The glossing an opacifying composition accordingto claim 8, wherein the ground calcium carbonate has a refraction indexof approximately 1.5 to 1.7.
 19. The glossing an opacifying compositionaccording to claim 14, wherein the pigment having a refractive index ofgreater than or equal 2.5 is selected from one or more of the following:titanium dioxide and/or zinc sulphide and/or zinc oxide, and preferablyis titanium dioxide.
 20. The glossing an opacifying compositionaccording to claim 19, wherein the pigment having a refractive index ofgreater than or equal 2.5 is titanium dioxide and the titaniumdioxide:ground calcium carbonate weight ratio is of 70:30 to 98:2, morepreferably the titanium dioxide:ground calcium carbonate weight ratio isof 85:15 to 90:10.
 21. A method of forming a clear coat composition,wherein water, nanoparticles and at least one binder are combined andthen dispersed in order to form the clear coat composition.
 22. Themethod according to claim 21, wherein the nanoparticles are dispersedwith one or more dispersants.
 23. A method of forming a glossing andopacifying composition wherein: a) at least one ground calcium carbonatehaving a D₅₀ (Mal) of between 0.05 and 0.3 μm is provided, b) at leastone pigment having a refractive index of greater than or equal 2.5 isprovided, c) at least one binder is provided, d) the ground calciumcarbonate of step a) is mixed with the pigment of step b) and the binderof step c).
 24. A substrate comprising the clear coat compositionaccording to claim
 1. 25. A coated substrate coated with a clear coatcomposition according to claim
 1. 26. The coated substrate according toclaim 24, wherein the substrate is selected from porous and non-poroussubstrates including papers, non-woven materials, textiles, leather,wood, concrete, masonry, metals, house wrap and other buildingmaterials, fiberglass, polymeric articles, personal protectiveequipment, carpets, textiles used in clothing, upholstery, tents,awnings, air bags, fabrics, yarns, and blends, whether woven, non-woven,or knitted, and whether natural, synthetic, or regenerated.
 27. Thecoated substrate according to claim 24, wherein the coated substrateincludes papers and non-wovens, fibrous materials, films, sheets,composites inks, printing binders, flock and other adhesives, andpersonal hair products including skin care, hair care, and nail careproducts, livestock and feed applications.
 28. The coated substrateaccording to claim 24, wherein the coating composition is applied to thesubstrate in an amount so as to form a layer having a thickness ofbetween 100 and 400 nm.
 29. A substrate comprising the glossing andopacifying composition according to claim
 8. 30. A coated substratecoated with a glossing and opacifying composition according to claim 8.31. The coated substrate according to claim 30, wherein the substrate isselected from porous and non-porous substrates including papers,non-woven materials, textiles, leather, wood, concrete, masonry, metals,house wrap and other building materials, fiberglass, polymeric articles,personal protective equipment, carpets, textiles used in clothing,upholstery, tents, awnings, air bags, fabrics, yarns, and blends,whether woven, non-woven, or knitted, and whether natural, synthetic, orregenerated.
 32. The coated substrate according to claim 30, wherein thecoated substrate includes papers and non-wovens, fibrous materials,films, sheets, composites inks, printing binders, flock and otheradhesives, and personal hair products including skin care, hair care,and nail care products, livestock and feed applications.
 33. The coatedsubstrate according to claim 30, wherein the coating composition isapplied to the substrate in an amount so as to form a layer having athickness of between 100 and 400 nm.
 34. The coated substrate accordingto claim 30, wherein the glossing and opacifying coating compositionprovides a gloss measured at 60° of greater than 70% and an opacity ofgreater than 97%.
 35. A method of forming a coated substrate coated witha clear coat composition, wherein a clear coat composition according toclaim 1 is applied to the substrate, preferably by coating, impregnatingor otherwise treating.
 36. The method according to claim 25, wherein thecoating composition is applied to the substrate in an amount so as toform a layer having a thickness of between 100 and 400 nm.
 37. Themethod according to claim 35, wherein the coated substrate is furtherdried and optionally cured.
 38. A method of forming a coated substratecoated with a glossing and opacifying composition, wherein a glossingand opacifying composition according to claim 8 is applied to thesubstrate preferably by coating, impregnating or otherwise treating. 39.The method according to claim 38, wherein the coating composition isapplied to the substrate in an amount so as to form a layer having athickness of between 100 and 400 nm.
 40. The method according to claim38, wherein the coated substrate is further dried and optionally cured.41. A colloidally stable aqueous dispersion comprising water, apolyester-polyurethane polymer binder and a plurality of substantiallydispersed submicron natural ground calcium-carbonate comprisingparticles.
 42. A composition comprising a binder containing submicronnatural ground calcium-carbonate comprising particles in a substantiallydispersed form.